- 2.1. Two-film theory. ...
- 2.2. Penetration theory. ...
- 2.3. Surface renewal theory.
What is the film theory in mass transfer?
The film theory has been extensively applied to describe the mass transfer in systems in which fluid phases are present. The theory considers that the resistance to mass transfer in a given turbulent fluid phase is present in a thin layer adjacent to the interface that is called a film (Seader et al., 2011).
What are the various theories of mass transfer?
- 2.1. Two-film theory. ...
- 2.2. Penetration theory. ...
- 2.3. Surface renewal theory.
What is meant by the term mass transfer?
Mass transfer describes the transport of mass from one point to another and is one of the main pillars in the subject of Transport Phenomena. Mass transfer may take place in a single phase or over phase boundaries in multiphase systems.
How many types of mass transfer exist?
Depending on the conditions, the nature, and the forces responsible for mass transfer, four basic types are distinguished: (1) diffusion in a quiescent medium, (2) mass transfer in laminar flow, (3) mass transfer in the turbulent flow, and (4) mass exchange between phases.
What is the two film theory?
The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film . Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients.
What drives mass transfer?
The driving force for mass transfer is usually a difference in chemical potential , when it can be defined, though other thermodynamic gradients may couple to the flow of mass and drive it as well. A chemical species moves from areas of high chemical potential to areas of low chemical potential.
What is the difference between mass transfer and diffusion?
The main difference between mass transfer and diffusion is that mass transfer may or may not involve a concentration gradient whereas diffusion does involve the movement of a solute down a concentration gradient.
What is the significance of film thickness in mass transfer?
depth of penetration of solute in liquid element3. the thickness of stagnant film that offers the same resistance to mass transfer as is actualy being offered under given hydrodynamic conditions.
What is convective mass transfer?
Convective mass transfer is the movement of material by the action of a fluid . ... Mass transfer – such as drying, evaporation or dissolution. Heat transfer – heat and mass transfer processes are analogous, and a mass transfer model may be more convenient to use.
What are the two factors that affect the rate of mass transfer?
Some important factors affecting the mass transfer rate, such as surfactant and its content, stirring speed, ratio of reagents, treating ratio and volume ratio of membrane phase to internal phase , have been studied. The breakage and the swelling of the emulsion have also been investigated.
How do you calculate mass transfer?
[In fact, the mass transfer equation is obtained based on the analogy with the heat transfer equation q = Q/A = h (DT); where DT is the temperature difference driving force for heat flow.
What are the modes of mass transfer explain with example?
Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, adsorption, drying, precipitation, membrane filtration, and distillation .
What are the three modes of mass transfer?
- Diffusion – defined as the spontaneous movement of any material from where it is to where it is not.
- Migration – the movement of charged particles in an electric field.
- Convection – movement of material contained within a volume element of stirred (hydrodynamic) solution.
What are the three types of mass diffusion?
Three types of diffusion are distinguished, viz., molecular, Brownian, and turbulent . Molecular diffusion occurs in gases, liquids, and solids; both diffusion of molecules of extraneous substances (impurities) and self-diffusion are observed. Molecular diffusion occurs as a result of thermal motion of the molecules.
Does temperature affect mass transfer?
Although temperature changes affected the mass transfer coefficients in the membrane phase as well as in the feed phase, the mass transfer coefficients in the membrane phase were found to be less than the mass transfer coefficients in the feed phase.
